Investigation of the asymmetric misfit dislocation morphology in epitaxial layers with the zinc-blende structure

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Abstract
Epitaxial growth of compound semiconductors on the (001) exhibits an asymmetry in the dislocation morphology in the two 〈110〉 directions for thicknesses near the critical thickness. The source of the asymmetry has been investigated by growth of a thickness wedge of p- and n-type GaAs0.95 P0.05 on GaAs by metalorganic chemical vapor deposition. The effect of misorientation on the resolved shear stress for each slip system has been calculated and eliminated as the source of the asymmetry. The thickness gradient was also eliminated as the source. A definitive correlation can be made between the asymmetry and the differences in the Peierls barriers of the two types of dislocations. The asymmetry results in two different critical thicknesses, one for each type of dislocation. The Peierls barriers are more similar in p-type material than in n-type material. In agreement with this, a reduced amount of asymmetry was observed in the p-type overgrowth as compared to the n-type. The nucleation barrier differences between the two types of dislocations are shown to be an unlikely source of the asymmetry.